Adler and Miller easefully tackle yet another aspect of mathematics with clear explanations and graphic interpretations that extend the topic of an earlier book of theirs, *Working with Fractions* (2007). Here the author draws the connection between fractions, decimals and percents using money as a convenient vehicle to express parts of a whole. The illustrator sets the action at a county fair with electric colors and sharp, two-dimensional edges. The price of goods at the fair serves to launch the discussion of how 89 cents becomes 89/100 becomes .89 becomes 89 percent. Gradually more complicated material is introduced—numerator, denominator, position relative to decimal point—and then how one finds decimals and percents when the denominator isn’t 100. Times when a particular use predominates is explained, and a few pop quizzes are administered to give readers a sense of grasp and accomplishment. The team’s sense of sheer fun gives the book significant propulsion, the county fair conveys an assuaging atmosphere for those with a touch of math anxiety and the quizzes offer an enjoyable challenge. Both straightforward and bouncy, a successful primer on parts. *(Picture book. 6-10)*